Aqueous and solid ammonium sulfate fertilizers and methods of producing

ABSTRACT

Aqueous and solid ammonium sulfate fertilizers derived from an organic feedstock and a mineral sulfate compound. The aqueous fertilizers have at least 3.5% nitrogen and at least 4% sulfur, and the solid fertilizers have about 21% nitrogen and about 24% sulfur. Methods for producing the fertilizers include preparing an organic feedstock by causing organic waste to undergo anaerobic digestion, removing solids from the organic feedstock to produce an organic liquid effluent, performing a distillation process on the organic liquid effluent to strip and concentrate a vapor that contains ammonia, carbon dioxide, and water and cool the vapor to produce a condensed solution containing ammonium bicarbonate and/or ammonium carbonate, and contacting the condensed solution with the mineral sulfate compound to cause a reaction therebetween and produce an aqueous ammonium sulfate product. An evaporation process can be performed on the aqueous ammonium sulfate product to produce a dry, solid ammonium sulfate product.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part patent application of co-pending UnitedStates patent application Ser. No. 17/096,533, filed Nov. 12, 2020,which claims the benefit of U.S. Provisional Application No. 62/934,279filed Nov. 12, 2019. The contents of these prior applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention generally relates to fertilizers and systems andprocesses capable of producing such fertilizers, and in particularorganic ammonium sulfate fertilizers from an effluent derived from oneor more organic sources.

High yields and healthy growth in food crops, gardens, and lawns requirea high soil nitrogen content. High ammoniacal nitrogen fertilizers arecommonly used to meet this need by delivering the necessary nitrogendirectly to soil and crops. However, most high ammoniacal nitrogenfertilizers currently available are synthetic fertilizers whichprecludes them from being used to produce organic crops, one of thefastest-growing sectors of the agricultural economy. In the UnitedStates, organic crops are regulated by the National Organic Program(NOP) standards developed under the Organic Foods Production Act of 1990(7 C.F.R. § 205), and the term “organic crops” is used herein consistentwith the NOP standards. By 2031, the demand for organic fertilizer withhigh nitrogen content is predicted to increase tenfold in the UnitedStates. Currently, very few companies offer an organic fertilizer thatmeets these needs.

Organic crops, specifically berries and legumes, require significantamounts of sulfur in order to be healthy. Sulfur promotes proteindevelopment in plants and enables plants to more efficiently utilizeother nutrients. Sulfur has previously been considered a “secondarynutrient” in fertilizers, whereas nitrogen, phosphorus, and potassiumhave previously been considered “primary nutrients.” However, recenttrends have led some growers to refer to sulfur as a “fourthmacronutrient” (i.e., a primary nutrient). This change is related to thefact that improving environmental stewardship in the United States hasreduced the incidence of acid rain, previously a means through whichsome crops have received sulfur. Synthetic crops generally receivesulfur from synthetic ammonium sulfate fertilizers which provide bothnitrogen and sulfur in the form of an ammonium sulfate compound.Currently, no known companies produce an ammonium sulfate fertilizerwith the potential to be certified organic. Therefore, most organiccrops receive sulfur from the application of composted manure which isinefficient compared to the effectiveness of ammonium sulfate products.

In view of the above, it can be appreciated that it would be desirableif products were available providing benefits associated with ammoniumsulfate fertilizers that is produced in accordance with the standards ofthe National Organic Program and therefore suitable for use as inputsfor organic crops.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides ammonium sulfate fertilizers derived fromorganic sources with significantly higher nitrogen and sulfur levelsthan other previously existing fertilizers produced from organicsources.

According to one aspect of the invention, an aqueous ammonium sulfatefertilizer is provided having at least 3.5% nitrogen and at least 4%sulfur, and derived from an organic feedstock and a mineral sulfatecompound.

According to another aspect of the invention, a solid ammonium sulfatefertilizer is provided containing about 21% nitrogen and about 24%sulfur, and derived from an organic feedstock and a mineral sulfatecompound.

Other aspects of the invention include methods for producing the aqueousand solid ammonium sulfate fertilizers noted-above with processes thatinclude the steps of preparing an organic feedstock that contains atleast one nitrogen compound by causing organic animal manure and/ororganic food waste to undergo anaerobic digestion, removing solids fromthe organic feedstock to produce an organic liquid effluent thatcontains at least one of ammonium and ammonia, performing a distillationprocess on the organic liquid effluent to strip and concentrate a vapormixture therefrom that contains ammonia, carbon dioxide, and water andcool the vapor mixture to produce a condensed solution containingammonium bicarbonate and/or ammonium carbonate, contacting the condensedsolution with the mineral sulfate compound to cause a reactiontherebetween and produce an aqueous ammonium sulfate product, and forthe solid ammonium sulfate fertilizers, performing an evaporationprocess on the aqueous ammonium sulfate product to remove watertherefrom and produce a dry, solid ammonium sulfate product.

Technical effects of the fertilizers described above preferably includethe ability to more efficiently provide sulfur to organic crops.

Other aspects and advantages of this invention will be appreciated fromthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically represents a process of producing liquid and dryammonium sulfate products derived from organic sources in accordancewith certain nonlimiting aspects of the invention.

FIG. 2 schematically represents a nonlimiting embodiment of a system forproducing an organic stabilized ammonium sulfate product in accordancewith certain nonlimiting aspects of the invention.

FIG. 3 schematically represents an isolated view of a product section ofthe system of FIG. 2.

FIG. 4 schematically represents an isolated view of an alternativeembodiment of the product section of the system of FIG. 2 in accordancewith certain nonlimiting aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following disclosure describes various aspects of systems andprocesses that are schematically represented in FIGS. 1 through 4 whichare suitable for producing organic ammonium sulfate fertilizers.Although the invention will be described hereinafter in reference toparticular features/functions schematically identified in the drawings,it should be noted that the teachings of the invention are not limitedto these particular features/functions, and the invention does notrequire all of the features/functions or the interfunctionalityrepresented in the drawings.

FIG. 1 schematically represents general steps that may be included insystems and processes for producing one or more products, including butnot limited to an organic, liquid ammonium sulfate fertilizer. Forconvenience, the processing steps will be described as being organizedinto three sections that include a pretreatment section, a distillationsection, and a product section. However, this should not be interpretedas limiting the scope of the invention as the processes could includeadditional or fewer steps, and/or the represented steps may becharacterized differently and/or include additional or fewer components.

In FIG. 1, the pretreatment section involves the processing of anorganic feedstock, referred to in FIG. 1 as a liquid organic waste, toyield a liquid organic waste filtrate (sometimes referred to herein asan “organic liquid effluent” or simply “effluent”) that containsammonium (NH₄ ⁺), or ammonia (NH₃), or both ammonium and ammonia. In theexample given, solids are removed from the organic feedstock byfiltration to produce the liquid organic waste filtrate. In thedistillation section, the liquid organic waste filtrate undergoes adistillation process that includes stripping from the liquid organicwaste filtrate a vapor mixture (“Tops Vapor”) that contains ammonia,carbon dioxide (CO₂), and water. The vapor mixture is concentrated andthen cooled and condensed to produce a condensed aqueous solutioncontaining ammonium bicarbonate ((NH₄)HCO₃) and/or ammonium carbonate((NH₄)₂CO₃). An ammonium bicarbonate product and/or ammonium carbonateproduct produced during the distillation process may be collected andremoved in this section. In the product section, the condensed aqueousammonium carbonate/bicarbonate solution is contacted with a stabilizingagent, which in the nonlimiting embodiment of FIG. 1 is represented asgypsum, to stabilize and concentrate stabilized products resulting froma reaction between the condensed liquid and the gypsum. The stabilizedproducts are identified in FIG. 1 as a calcium carbonate product and aconcentrated liquid ammonium sulfate product. Optionally, theconcentrated liquid ammonium sulfate product may be dried to produce adry ammonium sulfate product, such as ammonium sulfate fertilizer, and arecovered water vapor.

The term “stabilized” as used in reference to stabilized products refersto products that are not and do not contain gaseous ammonia, which wouldbe objectionable for safety and environmental reasons, and instead theammonia and nitrogen are contained in a stable compounds, such as astabilized ammonium sulfate compound. The stabilized products producedin the process of FIG. 1 are preferably “organic products,” which asused herein refer to products that are produced in accordance with thestandards of the National Organic Program (NOP) developed under theOrganic Foods Production Act of 1990 (7 C.F.R. § 205) such that theproducts can be approved for use as an input in organic crop production.Organic products can also refer to products and fertilizers approved bythird party organic certifying agencies using similar guidelines to theNational Organic Program. As an example, an organic, stabilized ammoniumsulfate product (e.g., ammonium sulfate fertilizer) as used hereinrefers to an ammonium sulfate product produced in accordance with theNOP standards with the potential to be approved for use in organic cropproduction and does not contain gaseous ammonia.

In view of the desire to produce organic products, it should beunderstood that the terms “organic feedstock” or “organically derivedfeedstock” refer to entirely natural source materials having containingammoniacal nitrogen from which the liquid organic waste filtrate(effluent) used herein is produced. The term “ammoniacal nitrogen” willbe used herein to refer to nitrogen that is contained in ammonium, andpreferably can be provided to a plant in a water-soluble form that isreadily available to the plant for use as a nutrient. These naturalsource materials may include, but are not limited to, animal manure(including cattle manure effluent and hog manure effluent), organic foodwaste, blood meal, feather meal, guano, bone meal, and wastewater from avariety of food and liquid processing operations. The organic feedstockis preferably anaerobically digested to remove pathogens and convertorganic matter into ammoniacal nitrogen. As known in the art, anaerobicdigestion is a collection of processes by which microorganisms breakdown biodegradable material (biomass) within a digester and in theabsence of oxygen. Within a digester, various types of bacteria may beused to break down the biomass into byproducts including biogas (e.g.,methane, carbon dioxide, etc.) and a liquid effluent, commonly referredto as digestate. Although synthetic substances may not necessarilyinhibit or have a significant effect on the processes disclosed hereinor their ability to produce high nitrogen fertilizers, to achieveorganic certification under the National Organic Program standards, thefeedstock is preferably digested while avoiding any contact with anysynthetic substances or materials, such as polymers that are commonlyused in certain solid separation processes for animal manure affluent.Effluents produced from these feedstocks and processed as describedherein preferably do not contain any suspended solids greater than 15microns, and preferably have a total suspended solids (TSS) of about2.5% or less.

Also consistent with the desire to produce organic products, additivesused in the process represented in FIG. 1 are also preferably organicproducts. As such, the gypsum (calcium sulfate dihydrate; a mineralcontaining calcium, sulfur, oxygen, and water in the form of CaSO₄·2H₂O)used in FIG. 1 is preferably certified as derived from an organic sourceunder relevant organic certifying institutions' standards relating toorganic crop inputs. For example, it is believed that only mined gypsummay be used in the process in order for the resulting ammonium sulfateproduct to be an organic product. As such, the processes disclosedherein preferably only use mined mineral gypsum. Other mined mineralcompounds containing sulfate such as Epsom salt (magnesium sulfate) maybe used in addition to or as an alternative to gypsum. Therefore, theuse of the terms “natural sources” and “organic sources” herein refer toboth the additives and the liquid organic waste filtrate.

FIG. 2 schematically represents a nonlimiting embodiment of a system andprocess for producing an organic stabilized ammonium sulfate productcapable of high ammoniacal nitrogen and sulfur contents. In thisembodiment, organic waste material is sourced from an animal feedlot 1and processed in an anaerobic digester 2 to produce a digestate. Thedigester 2 may be a component of the system represented in FIG. 2 or thedigestate produced therefrom may be delivered from a remote operationcomprising the digester 2. Alternatively, a lagoon storage may be usedinstead of the digester 2.

Suspended solids are preferably removed from the digestate, for example,to produce an effluent having the aforementioned maximum suspendedsolids particles size of not greater than 15 microns and a totalsuspended solids (TSS) of about 2.5% or less. In FIG. 2, the equipmentrepresented for removing solids from the digestate include a centrifuge3 and filter unit 4, for example, a fiber press, a screen, orultrafiltration equipment, though time and gravity in a lagoon may byitself be adequate. A combination of two or more filtration methods ispreferred to ensure adequate solids removal. The resulting effluent islikely to be at a temperature of about 100° F. (about 35° C.) and maycontain about 1800 ppm ammonium, ammonia, and other forms of nitrogen,as well as hydrogen sulfide (H₂S), carbon dioxide, other volatileorganics, and certain levels of calcium, iron, magnesium, sodium,potassium, phosphorus, manganese, etc.

The effluent is generally the product of a pretreatment section of thesystem of FIG. 2, and is transferred with a pump 5 to a distillationtower 15 that forms part of a distillation section of the system. Theeffluent is preferably at an elevated temperature when it is enters thedistillation tower 15. For this reason, a heat exchanger 6 may be usedto raise the temperature of the effluent to over 90° F. (about 30° C.),for example at least 180° F. (about 80° C.), and more preferably in therange of 180° F. to 200° F. (80° C. to 95° C.).

The distillation tower 15 is preferably a packed media column, althoughother distillation methods such as sieve trays may be used. Within thedistillation tower 15, the heated effluent enters a stripping section 7configured to strip and remove ammonia from the effluent. In thenonlimiting embodiment represented in FIG. 2, a boiler 31 is used togenerate steam for this purpose. The steam is preferably at a pressureof least 15 psi (about 100 kPa) and at least 250° F. (120° C.). Theammonia is removed from the effluent by provoking the effluent to coverthe packed media, which causes gaseous ammonia to pass through thepacked media and escape the effluent. The gaseous ammonia isconcentrated in a concentration section 8 of the distillation tower 15located above the stripping section 7 before exiting the tower 15through a conduit 11 at the top of the tower 15.

The gaseous ammonia is entrained in a vapor mixture (Tops Vapor inFIG. 1) that also contains carbon dioxide gas and water vapor, and mayfurther include hydrogen sulfide and other volatile compounds. The vapormixture is preferably at a temperature of between 150° to 212° F. (35°C. to 100° C.), more preferably 180° to 200° F. (80° C. to 95° C.), mostpreferably about 190° F. (90° C.). The vapor mixture preferably has anammonia concentration above 10%, more preferably above 12%, and mostpreferably above 15%.

The vapor mixture is conducted to a condenser 12 where the vapor mixtureis condensed to yield a condensed aqueous solution that contains aqueousammonia, ammonium bicarbonate, and/or ammonium carbonate. The condenser12 is represented in FIG. 2 as a reflux condensing loop having a coolingcoil 13 fed with water, air, or glycol coolant 13 a. Though representedas external of the tower 15, condensers incorporated into the top of thetower 15 are also foreseeable. In the embodiment shown, the condenser 12is configured to recycle a portion of the condensed aqueous ammoniacalnitrogen solution back to the tower 15 through a pump 14 to raise theconcentration of ammonia within the concentration section 8 to increasethe efficiency of ammonia removal from the effluent. The tower 15 ispreferably operated at an ammonia removal efficiency of at least 80%,more preferably 90%, and most preferably 95% or more.

The tower 15 also releases a liquid mixture 9 (bottoms liquid in FIG. 1)that includes, without limitation, condensed steam and heated effluent.The heated liquid mixture 9 exits through a tank 10 located at a lowerend of the tower 15 and passes through the heat exchanger 6 to transferheat to the effluent entering the system. After the heat exchanger 6,the liquid mixture 9 may be removed to a lagoon 39 for storage, forexample, if the system is constructed at a Confined Animal FeedingOperation or other operation that has use of the liquid mixture 9.

The distillation tower 15 is preferably constructed to maintain organicprocess controls as defined by the National Organic Program and/or otherrelevant institutions. This includes, without limitation, the totalabsence of synthetic substances in areas that come into contact with theeffluent and product as well as precautions to ensure that potentialspills or leaks cannot introduce synthetic materials to the system.Additionally, organic process controls are preferably applied to themaintenance, operation, and sanitation of the equipment. Automation mayalso be used in the system to efficiently regulate the temperature andpressure inside the system.

A fraction of the vapor mixture that enters the condenser 12 and afraction of the condensed aqueous solution condensed within thecondenser 12 are shown in FIG. 2 as being separately transported to aproduct section of the system, and particularly to a water bath within atank 17 that contains water and dissolved gypsum, which serves tostabilize the ammonium in the vapor mixture and allows ammonium in thecondensed aqueous solution to remain in a liquid form as ammoniumcarbonate and/or ammonium bicarbonate when mixed with water. The tank 17facilitates a reaction between the gypsum and the ammoniumbicarbonate/carbonate, which as shown in Equations 1 and 2 producescalcium carbonate (CaCO₃) and a stabilized ammonium sulfate ((NH₄)₂SO₄)product. In certain embodiments, the vapor mixture exiting the condenser12 may be condensed before entering the water bath. In such anembodiment, the vapor mixture takes the form of a liquid ammoniumcarbonate solution when it enters the water bath.

CaSO₄·2H₂O+(NH₄)₂CO₃→CaCO₃+(NH₄)₂SO₄+2H₂O  Eq. 1

CaSO₄·2H₂O+2(NH₄)HCO₃→CaCO₃+(NH₄)₂SO₄+3H₂O+CO₂  Eq. 2

FIG. 3 represents an isolated view of the product section of the systemof FIG. 2. As seen in FIGS. 2 and 3, the vapor mixture drawn from thecondenser 12 is transported through a conduit 38 and then a heatexchanger 40 into the water bath of the tank 17. The concentration ofammonia in the vapor mixture at this point in the system preferably doesnot exceed 18% by weight. As represented, the system includes at least asecond tank 19 connected to the first tank 17. Each tank 17 and 19 ispreferably pressurized and contains a mechanical mixing mechanism 17 aand 19 a to mix the gypsum with the dissolved ammonium carbonate of thecondensed aqueous solution (collectively referenced by 41 and 42 intanks 17 and 19, respectively) inside the tanks 17 and 19.

The first tank 17 contains a relatively small amount of gypsum, whichquickly reacts with the ammonium carbonate in the condensed aqueoussolution. The first tank 17 also includes a small amount of ammoniumsulfate and a small amount of calcium carbonate as a result of thereaction of Equation 1. The calcium carbonate formed in the tank 17exits the tank 17 via a circulation stream 29 from which the calciumcarbonate is removed with a filter 30. The resulting filtered calciumcarbonate stream 44 is dried with a dryer/evaporator 33 to produce driedcakes thereof to be stored in a storage vessel 34. A filtrate slurry 32containing the remaining ammonium carbonate/bicarbonate and ammoniumsulfate originally in the circulation stream 29 enters the second tank19, which contains a higher concentration of gypsum than the tank 17 asa result of gypsum being directly added to the tank 19 from a gypsumsource 24. In addition, excess gases 18 from the first tank 17 may bediverted to the second tank 19.

Within the second tank 19, the gypsum reacts quickly with the ammoniumcarbonate, so that the reaction products within the tank 19 areprimarily ammonium sulfate and calcium carbonate. The resulting slurrystream 20 containing ammonium sulfate and calcium carbonate exits thetank 19, and a stabilized product 35 (primarily an ammonium sulfatesolution) is removed from the slurry stream 20 with a filter 27 beforebeing sent to concentration stages of the process. In FIGS. 2 and 3, thestabilized product 35 may be transported to a liquid storage tank 21 orfurther dried with a dryer/evaporator 36 to produce solid ammoniumsulfate crystals and stored in storage vessel 37. A slurry 28 containinggypsum, calcium carbonate, and ammonium sulfate is also shown as beingdrawn from the second tank 19 and transported to the first tank 17 to beused in the reactions that occur there. Excess gases 25 such as carbondioxide (CO₂) 25 a and hydrogen sulfide (H₂S) 25 b may be removed fromthe second tank 19. Optionally, a production system 26 may be includedto produce iron sulfide from the excess gases 25. The stabilized product35 collected in the tank 21 may be packaged as a liquid ammonium sulfatesolution fertilizer 22. Alternatively or in addition, a fraction of thecondensed aqueous solution produced by the condenser 12 may be collectedin a storage tank 16 and packaged as a liquid fertilizer 22.

FIG. 4 represents an isolated view of an alternative embodiment of theproduct section of the system of FIG. 2. In this embodiment, representedas a batch process, the vapor mixture transported by the conduit 38 isdrawn through a compression pump 112 and delivered to a single mixingtank 114, instead of the series of tanks 17 and 19 shown in FIGS. 2 and3. The mixing tank 114 is preferably a pressurized tank and contains amechanical mixing mechanism 115 to mix the vapor mixture with gypsumfrom a gypsum source 111 and dissolved ammonium carbonate of thecondensed aqueous ammoniacal nitrogen solution drawn from the condenser12. The condensed aqueous ammoniacal nitrogen solution and gypsum arerespectively represented by 117 and 118 in the tank 114. The temperaturein the tank 114 is preferably 90° F. to 130° F. (about 30° C. to 55°C.), more preferably 100° F. to 120° F. (about 35° C. to 50° C.), andmost preferably about 105° F. (about 40° C.). The mechanical mixing inthe tank 114 is preferably maintained at about 200 RPM, preferably for aduration of 4 to 12 hours, more preferably 6 to 10 hours, and mostpreferably about 8 hours. The batch process is not necessarily limitedto a single tank 114 and additional embodiments can include multiplevessels with mechanical mixing in each. Optionally, a water-cooledcondenser 116 may be coupled to the tank 114. A stabilized product(primarily an ammonium sulfate solution) produced in the tank 114 may beremoved and stored in a liquid storage tank 120, from which it mayundergo further processing such as drying as described in reference toFIGS. 2 and 3.

In all embodiments of the water bath (tanks 17, 19, and 114), theresulting liquid is removed and heated to increase the concentration ofammonia and sulfur in the liquid. Although not shown, the ammoniumsulfate solution can be diverted to a mechanical dryer to evaporate allthe water off the product to create solid ammonium sulfate crystalsusing components similar to those represented in FIG. 3, which can beused as a solid ammonium sulfate fertilizer. The drying processpreferably creates water vapor, which can be diverted for use in theearlier stages of the process, preferably the distillation section.

The systems and processes described above produce a liquid or solidorganic fertilizer containing soluble ammoniacal nitrogen and organicsulfur. The majority of organic fertilizers currently commerciallyavailable contain relatively low levels of nitrogen in forms that areslowly released over the course of weeks or months. In contrast, theammoniacal nitrogen in the products produced by the processes describedherein is immediately available to plants/crops upon contact with thefertilizer.

The liquid fertilizer produced preferably has a pH between 4.5 and 6.5,most preferably about 5. Water is preferably present in the liquidfertilizer in an amount of at most 83.5 wt %, for example, about 67 wt %of the product. The liquid fertilizer preferably contains at least 16.5%dissolved solids, for example, about 33% dissolved solids, and maycontain trace amounts of calcium carbonate, calcium sulfate (e.g.,gypsum), and other mineral residues. The fertilizer is preferably freeof or substantially free of pathogens, nitrates, and phosphate. Thenitrogen in the liquid fertilizer is preferably in concentrationsbetween 3.5 and 9%, more preferably 6 to 8% and, most preferably about7%. The sulfur in the liquid fertilizer is preferably in a concentrationof 4 to 10%, more preferably 7 to 9%, and most preferably about 8%. Thenitrogen-to-sulfur ratio in the liquid fertilizer is preferably 7:8,that is, the nitrogen:sulfur by weight ratio of ammonium sulfate. Anynitrogen and sulfur outside of the 7:8 ratio may reflect changes in theamount of gypsum added to the ammonium carbonate/bicarbonate solutionand such difference may be due to undissolved ammoniacal nitrogenremaining in the product. In certain embodiments, the liquid fertilizermay have a nitrogen-to-phosphorus-to-potassium-to-sulfur (N—P—K—S) ratioof 7:0:0:8.

The dry fertilizer produced preferably contains about 21% nitrogen andabout 24% sulfur. In certain embodiments, the dry fertilizer may have anitrogen-to-sulfur ratio of 21:24. In certain embodiments, the dryfertilizer may have a nitrogen-to-phosphorus-to-potassium-to-sulfur(N—P—K—S) ratio of 21:0:0:24. The higher nitrogen content in the dryfertilizer may lead organic certifying agents to require the fertilizerto be mixed with compost or only be used to supply 20% of a crop'snitrogen needs during a single harvest.

The fertilizer produced is preferably produced in accordance with thestandards of the National Organic Program and other relevant organiccertifying institutions in order for the fertilizer to be approved as aninput in organic crop production.

The resulting liquid fertilizer is excellent for providing bothsignificant levels of nitrogen and sulfur to organic crops in a singleconcentrated product. The fertilizer provides a more cost competitivecost-per-pound of nitrogen as opposed to other commercially availableproducts. The nitrogen is in a water soluble form easily taken up byplants, a faster release time than nitrogen found in compost or otherorganic fertilizers which have nitrogen release times stretching overseveral weeks to even months. The sulfur in the resulting liquidfertilizer is believed to be a preferred concentration for specialtyorganic crops such as berries and legumes. In particular, the berrymarket is currently one of the fastest growing sectors of the organicsindustry and current limitations of organic fertilizers have increasedthe overhead costs of growing organic berries. An organic ammoniumsulfate product such as the fertilizers disclosed herein are believed tohave the potential to reduce these overhead costs and encourageinnovation in the organics industry. Traditional row crops such as wheatmay also benefit from the product described therein.

The fertilizer produced is concentrated and easy to transport comparedto other organic fertilizers on the market including compost, feathermeal, urea, and other products, reducing the carbon footprint of organiccrop production. The dry fertilizer can also be mixed with currentcomposts and other fertilizers on the market, necessitating smalleramounts of compost and other fertilizers to be transported.

Additionally, the fertilizer produced sequesters carbon in the form ofcalcium carbonate during the ammonium sulfate production process. Thecarbon sequestered would otherwise be released into the atmosphere ifthe effluent used in the system was disposed of otherwise. The carbonsequestered amounts to roughly 1.5 pounds (about 0.7 kg) of carbondioxide per pound (about 0.5 kg) of nitrogen in the fertilizer. Thisequates to roughly 1.5 carbon credits per 3,450 gallons (about 13,060 L)of fertilizer applied. This sequestration provides for a method ofenvironmental management on the animal feedings operations where theorganic waste filtrate required by the present invention can be sourcedfrom anaerobically digested manure.

In investigations leading to aspects of the present invention, theabove-noted process was used in the production of dry ammonium sulfateusing an automated 24 foot (about 7.3 m) tall distillation towerconnected to a 110,000 BTU (about 116,056 kJ) boiler. Specifically, 0.3gallons (about 1.14 L) per minute of digested dairy cow manure effluentcontaining 1800 ppm ammonia filtered to 15 microns was preheated to 150°F. (about 65° C.) using a heat exchanger and then further heated to 180°F. (about 80° C.) using another heat exchanger before entering thetower. The second heat exchanger used heat captured from the Bottomsexiting the distillation tower at approximately 210° F. (about 100° C.).

The 180° F. (80° C.) effluent was pumped to the distillation tower to apoint 16 feet (about 4.9 m) high on the tower. The tower was a packedmedia distillation column with a six inch (about 15 cm) diameter in theammonia stripping portion. Live steam from the boiler was injected intothe tower at 12 to 15 psi (about 82 to about 104 kPa) above the bottomscollection tank at the base of the tower. The ammonia from the effluentwas stripped in the lower 16 feet (about 4.9 m) of the tower and thenconcentrated in the upper 8 feet (about 2.5 m) of the tower. Theconcentration portion had a diameter of 6 inches (about 15 cm) at thefeed line to 2 inches (about 5 cm) at the top. CO₂ and H₂S was alsostripped from the manure in the column. A mixture of ammonia, CO₂, H₂S,and water vapor exited the top of the tower as a vapor mixture. Thevapor mixture exited the tower at approximately 180° F. (about 80° C.).

The concentration of the ammonia occurred using internal refluxcondensation in jacketed cooling cans in the tower. Cold groundwater wasrun through the jacketed portions and the flow of the water was managedby control valves. The distilled vapor mixture was piped into amultistage gypsum slurry bath resulting in the production of ammoniumsulfate and calcium carbonate slurry. The gypsum bath was maintained atapproximately 110° F. (about 43° C.). The calcium carbonate was filteredout of the slurry resulting in an ammonium sulfate liquid. The calciumcarbonate was dried resulting in a calcium carbonate cake.

Analysis of the liquid ammonium sulfate product concluded that theproduct contained at least 3% ammoniacal nitrogen and at least 3.4%sulfur. Lab analysis showed that there was more than an 80% ammoniaremoval efficiency from the effluent. A portion of the liquid ammoniumsulfate product was evaporated and dried to produce dry ammonium sulfatecrystals.

While the invention has been described in terms of specific embodiments,it is apparent that other forms could be adopted by one skilled in theart. For example, the physical configuration of the system could differfrom that shown, and materials and processes/methods other than thosenoted could be used. Therefore, the scope of the invention is to belimited only by the following claims.

1. An aqueous ammonium sulfate fertilizer having at least 3.5% nitrogenand at least 4% sulfur, and derived from an organic feedstock and amineral sulfate compound.
 2. The aqueous ammonium sulfate fertilizer ofclaim 1, wherein the aqueous ammonium sulfate fertilizer containsnitrogen and sulfur in a 7:8 ratio.
 3. The aqueous ammonium sulfatefertilizer of claim 1, wherein the aqueous ammonium sulfate fertilizercontains 7% nitrogen and 8% sulfur.
 4. The aqueous ammonium sulfatefertilizer of claim 1, wherein the aqueous ammonium sulfate fertilizerincludes at least 16.5 wt % dissolved solids.
 5. The aqueous ammoniumsulfate fertilizer of claim 1, wherein the aqueous ammonium sulfatefertilizer is substantially free of pathogens.
 6. The aqueous ammoniumsulfate fertilizer of claim 1, wherein the aqueous ammonium sulfatefertilizer comprises at most 83.5 wt % water.
 7. The aqueous ammoniumsulfate fertilizer of claim 1, wherein the aqueous ammonium sulfatefertilizer meets the standards for approval as an input in organic cropproduction under the National Organic Program.
 8. The aqueous ammoniumsulfate fertilizer of claim 1, wherein the aqueous ammonium sulfatefertilizer has a N—P—K—S ratio of 7-0-0-8.
 9. The aqueous ammoniumsulfate fertilizer of claim 1, wherein the mineral sulfate compoundincludes mined gypsum (calcium sulfate).
 10. The aqueous ammoniumsulfate fertilizer of claim 1, wherein the mineral sulfate compound ismined Epsom salt (magnesium sulfate).
 11. The aqueous ammonium sulfatefertilizer of claim 1, wherein the aqueous ammonium sulfate fertilizercontains residues of calcium carbonate, calcium sulfate, and/or othermineral additives.
 12. The aqueous ammonium sulfate fertilizer of claim1, wherein the aqueous ammonium sulfate fertilizer produced by a processcomprising the steps of: preparing an organic feedstock that contains atleast one nitrogen compound by causing organic animal manure and/ororganic food waste to undergo anaerobic digestion; removing solids fromthe organic feedstock to produce an organic liquid effluent thatcontains at least one of ammonium and ammonia; performing a distillationprocess on the organic liquid effluent to strip and concentrate a vapormixture therefrom that contains ammonia, carbon dioxide, and water, andcool the vapor mixture to produce a condensed solution containingammonium bicarbonate and/or ammonium carbonate; and contacting thecondensed solution with the mineral sulfate compound to cause a reactiontherebetween and produce an aqueous ammonium sulfate product.
 13. Asolid ammonium sulfate fertilizer containing about 21% nitrogen andabout 24% sulfur, and derived from an organic feedstock and a mineralsulfate compound.
 14. The solid ammonium sulfate fertilizer of claim 13,wherein the solid ammonium sulfate fertilizer is substantially free ofpathogens.
 15. The solid ammonium sulfate fertilizer of claim 13,wherein the solid ammonium sulfate fertilizer meets the standards forapproval as an input in organic crop production under the NationalOrganic Program.
 16. The solid ammonium sulfate fertilizer of claim 13,wherein the solid ammonium sulfate fertilizer has a N—P—K—S ratio of21-0-0-24.
 17. The solid ammonium sulfate fertilizer of claim 13,wherein the mineral sulfate compound includes mined gypsum (calciumsulfate).
 18. The solid ammonium sulfate fertilizer of claim 13, whereinthe mineral sulfate compound is mined Epsom salt (magnesium sulfate).19. The solid ammonium sulfate fertilizer of claim 13, wherein the solidammonium sulfate fertilizer is crystalline ammonium sulfate.
 20. Thesolid ammonium sulfate fertilizer of claim 13, wherein the solidammonium sulfate fertilizer is produced by a process comprising thesteps of: preparing an organic feedstock that contains at least onenitrogen compound by causing organic animal manure and/or organic foodwaste to undergo anaerobic digestion; removing solids from the organicfeedstock to produce an organic liquid effluent that contains at leastone of ammonium and ammonia; performing a distillation process on theorganic liquid effluent to strip and concentrate a vapor mixturetherefrom that contains ammonium bicarbonate and cool the vapor mixtureto produce a condensed solution containing ammonium bicarbonate and/orammonium carbonate; contacting the condensed solution with the mineralsulfate compound to cause a reaction therebetween and produce an aqueousammonium sulfate product; and performing an evaporation process on theaqueous ammonium sulfate product to remove water therefrom and produce adry, solid ammonium sulfate product.